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This project sounds kind of masochistic but the idea is to bootstrap Rust from tinycc, and have traceability down to the lowest level assembly code. There is a step missing though? Tinycc is written in C after all.
I think it would make more sense to bootstrap from a small Lisp written in assembly language, if the traceability goal is worthwhile at all. There is nothing special about C.
The main thing is that TinyCC has already been bootstrapped.
Check out this page on bootstrappable.org. Basically they start with a 200 something byte binary (hex0) that can act as an assembler, then using a bunch of layers of tools and compilers you can bootstrap a whole system. I think they use stage0 to build M2-Planet, use that to build GNU Mes, and use that to build TinyCC.
So a project like this fits neatly into that bootstrapping path. It could be done other ways, but starting from a fairly complete C compiler makes it a lot easier than building an entire path from scratch.
There is nothing special about C.
I wish that were true, but isn’t it somewhat wishful thinking? Even an assembly-language Lisp would require an operating system in order to build a functioning compiler, wouldn’t it? And operating system APIs are in C.
Edit: more importantly, as the post explains, the special thing about C is the existence of TinyCC.
In principle you could start from hand assembly. Look up “sectorlisp” as a lowest level option. Or you could start from Forth, which is traditionally implemented using very simple methods. The blog post really doesn’t make clear what problem the author is trying to solve. It gives some general description but leaves a lot to be guessed at.
Then there is the question of where the CPU is supposed to come from. Any modern one was designed using lots of mysterious CAD tools. Maybe scrounge a vintage Z80 out of an old Timex-Sinclair or something?
The author doesn’t explain exactly what their interest in bootstrapping is, but the goal is pretty explicit:
So, for me, it would be really nice if there was a Rust compiler that could be bootstrapped from C. Specifically, a Rust compiler that can be bootstrapped from TinyCC, while assuming that there are no tools on the system yet that could be potentially useful.
The deeper reasoning is still not explained. C is just terrible for this. Rust is very complicated and writing a new implementation is a big project even in good languages. So using C seems tragic.
I’m going to go further and say that TinyCC isn’t bootstrapped either, since the compiler writer’s thought processes aren’t bootstrapped. You would have to use something like CompCert (i.e. all the reasoning that the programs works is embedded in the program and machine checked) and bootstrap that. It is probably doable, but not as a 1 person hobby project.
Okay. That’s just imposing a different (and at least equally arbitrary, if not moreso) definition of bootstrapping. Why does it matter that the author didn’t explain their “deeper reasoning” for having an interest in bootstrapping, or the Bootstrappable Builds project specifically? If you feel like that project isn’t meeting a sufficient bar for what counts as “bootstrapping”, or that using C as the first high-level language they bootstrap is “tragic”, take it up with that project, I guess.
I will take a look at the bootstrapping project page, but “bootstrappability” is a philosophical notion whose extent depends on what you are trying to get from it. Certainly someone who pursues it should give that some thought and reach a conclusion, rather than just following a recipe on some web site. So that’s the deeper reasoning I felt was missing.
As for C being terrible, well, why would I want to take that up with anyone? It’s simply that we know from 50 years of experience with C that writing bug-free C programs, or noticing the existence of bugs in them, is extremely difficult. If someone decides to use it for bootstrapability anyway, xkcd.com/386 would seem to apply.
collapseos.org (which uses Forth) might also be of some interest, though I think that was another questionable decision. Real transparency and boostrapability requires that the reasoning process be written out and matched up with the code. C does a pretty poor job of that compared to some alternatives.
Then there is the question of where the CPU is supposed to come from. Any modern one was designed using lots of mysterious CAD tools. Maybe scrounge a vintage Z80 out of an old Timex-Sinclair or something?
Didn’t Rust itself used to have a compiler written in a different language? I mean, obviously it would’ve had to at some point but I think I remember reading about them abandoning it once they didn’t need it. Why not use that?
You can technically do it, but it’s a convoluted path. The article talks about it. Basically to bootstrap that way you need to go through a lot of versions of rust, compile rust 0.7 in scala, compile scala in scheme, and compile scheme in C using gcc. For gcc you need to compile a chain of versions back to when it was written in C instead of C++, plus the whole TinyCC bootstrapping path.
Ah okay. The article was a little over my head so I mostly skimmed it. This makes sense what you’re saying though. It’s easy to forget the level of bootstrapping they’re trying to do is all the way to assembly.
It’s the sort of thing if you think about too long you’ll get paranoid and start using Gentoo exclusively lol.
compile rust 0.7 in scala
Not sure if there was another rewrite, but AFAIK (and the article agrees with me) rustc was originally written in Ocaml
If you had read the article, you’d know!
I wonder if someone’s working on this from the other end. Like, instead of porting mrust from gcc to tinycc, port rust 1.79 from 1.78 to 1.1.
